NIH study shows even moderate exercise substantially cuts risk

Tuesday, May 20, 2014

Exercise alone may help prevent gestational diabetes—which occurs in women during pregnancy—from progressing to Type 2 diabetes in the time after pregnancy, according to a study by researchers at the National Institutes of Health and other institutions.

Women who have had gestational diabetes are at higher risk for Type 2 diabetes. Previous research has shown that these women can reduce their Type 2 risk by adopting a comprehensive program of exercise and healthy eating, and, if needed, treatment with the drug metformin. The results of the current study are the first to show that, the greater the level of physical activity, the less likely Type 2 diabetes was to occur. The researchers observed this pattern regardless of the women’s diet and level of body fat—both factors also associated with an increased risk of Type 2 diabetes

“Women at high risk for Type 2 diabetes because they once had gestational diabetes are best advised to eat healthy, exercise regularly, and control their weight,” said the study’s senior author, Cuilin Zhang, M.D., Ph.D., in the Division of Intramural Population Health Research of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). “However, for those who may even be obese or have not adopted healthy eating habits, moderate or vigorous exercise alone may help to reduce the risk substantially.

The study appears in JAMA Internal Medicine. In addition to support from the NICHD, the study was also funded by two other NIH institutes, the National Institute of Diabetes and Digestive and Kidney Diseases, and the National Cancer Institute.

The researchers found that women who did 150 minutes of moderate exercise each week—a half hour of walking each day for 5 days—cut their risk of Type 2 diabetes by 47 percent when compared to those who did not exercise. The researchers found more substantial reductions in risk for those who spent even more time exercising. In general, the more the women exercised, and the harder they exercised, the less likely they were to progress to Type 2 diabetes.

Gestational diabetes affects about 5 percent of all pregnancies. In women with gestational diabetes, the body does not use insulin efficiently and the level of blood sugar, or glucose, increases. The high blood sugar levels may result in babies growing too large, which may lead to injuries during birth, or require a cesarean delivery. Infants born to mothers with gestational diabetes are also at risk for preterm birth, which increases their risk for death in the first year of life, visual and learning difficulties, and neurological problems such as cerebral palsy.

For the mother, gestational diabetes increases the risk of high blood pressure, and of preeclampsia, a potentially life-threatening complication of pregnancy. Among women with gestational diabetes, up to 35 to 60 percent r develop type 2 diabetes, within 20 years after giving birth. Complications of Type 2 diabetes include heart disease, and damage to the eyes, kidney, and nerves.

To conduct their study, Dr. Zhang and her colleagues analyzed information from 4554 women participating in the Nurses’ Health Study II who reported they had been diagnosed with gestational diabetes, which is a part of NIH’s ongoing Diabetes & Women’s Health Study, which investigating factors that determine the risk of Type 2 diabetes among women who had gestational diabetes. Of these women, 635 eventually developed Type 2 diabetes. The women were 22 to 45 years old when they enrolled in the study. Every two years they responded to questions on their general health, pregnancy status, and lifestyle habits, and every four years they completed a comprehensive survey about the kinds of food and drink they consumed.

“This study shows a clear dose-effect association between physical activity and Type 2 diabetes risk among women who had gestational diabetes.” said Dr. Wei Bao, the first author, a visiting post-doctoral fellow at NICHD. “The more physical activity the women engaged in after giving birth, the less likely they were to develop Type 2 diabetes.

The researchers expressed the time the women spent exercising in terms of a numerical concept they referred to as a Metabolic Equivalent hours (METs). They defined a metabolic equivalent hour as the amount of energy typically extended for a particular activity. The figure is based on a ratio of oxygen taken in versus calories expended. Each weekly increase of 5 METs—equal to about 100 minutes per week of moderate intensity physical activity or 50 minutes per week of vigorous physical activity— was associated with a 9 percent reduction in Type 2 diabetes.

The researchers also found that time spent watching television was associated with an increased Type 2 diabetes risk. Watching television, the researchers wrote, often replaces time that might be spent in physical activity, and is associated with mindless eating.

“Finally, while watching TV, women may be influenced by commercial food advertisements for nutrient-poor, high calorie foods,” the researchers wrote.

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About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute’s website at http://www.nichd.nih.gov/.

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov.